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 431 
 WTNT43 KNHC 160843
 TCDAT3
 
 Tropical Storm Helene Discussion Number  36
 NWS National Hurricane Center Miami FL       AL082018
 500 AM AST Sun Sep 16 2018
 
 Helene's cloud pattern is certainly looking less and less like a
 tropical cyclone this morning.  Based on conventional satellite
 imagery and AMSU data, Helene is quickly undergoing an extratropical
 transition, and this dynamic process is expected to be completed
 later today, as the cyclone moves away from the Azores.  The
 initial intensity is lowered to 45 kt, and is based primarily on
 2326 UTC ASCAT-A wind retrievals.  Cold (22C) sea surface
 temperatures and strong westerly shear will continue to disrupt
 Helene's vertical structure and should cause the cyclone to
 complete the extratropical transition in 12 hours, or sooner.
 
 The initial motion is estimated to be northeastward, or 50/22 kt,
 within the ferocious mid-latitude westerlies.  The global models are
 in remarkably good agreement with Helene accelerating northeastward
 and becoming absorbed in a large baroclinic zone extending over
 northern United Kingdom in 72 hours, and the official forecast
 reflects this scenario.
 
 Earlier 2326 UTC METOP-A ASCAT scatterometer data indicated that the
 34 kt and 50 kt wind radii, particularly in NW and NE quadrants, had
 decreased considerably.  Accordingly, an adjustment was made on this
 advisory.
 
 Interests in those locations should consult products from their
 local meteorological service for information about potential impacts
 from Helene. Local forecasts and warnings for the UK can be found on
 the website of the UK Met Office athttps://www.metoffice.gov.uk/.
 Local forecasts and warnings for Ireland can be found on the website
 of Met Eireann at https://www.met.ie/.
 
 
 FORECAST POSITIONS AND MAX WINDS
 
 INIT  16/0900Z 42.5N  28.4W   45 KT  50 MPH
  12H  16/1800Z 44.5N  24.7W   45 KT  50 MPH...POST-TROP/EXTRATROP
  24H  17/0600Z 47.4N  18.1W   45 KT  50 MPH...POST-TROP/EXTRATROP
  36H  17/1800Z 50.8N  10.8W   45 KT  50 MPH...POST-TROP/EXTRATROP
  48H  18/0600Z 55.1N   3.7W   40 KT  45 MPH...POST-TROP/EXTRATROP
  72H  19/0600Z...ABSORBED BY A FRONT
 
 $$
 Forecaster Roberts
 
 
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